Thanks in advance for any assistance rendered!
I have a 1994 F150 with the 4R70W transmission. The transmission hits hard going into 2nd gear and seems normal after that. There are times when it will NOT go into 2nd but usually I can mess with the throttle to assist it and finally it'll make the shift. Seems that when I first start to drive it from a cold start it works fairly well then degrades. I have also observed the occasion where it will go into 2nd but slips, as I can increase RPM but the speed will not increase.
I have changed fluid, filter, shift sensor, and shift solenoid. The old fluid didn't appear too bad. Bright red maybe a little darker than normal. I did have some very fine grayish granular sludge around the magnet in the pan but not nearly as much as I've observed in some of the videos I've seen. I can manual shift into 2nd with no issues it seems. D is the problem.
Again thanks for your advisement!

 

There are several shift solenoids in the tranny, either you still have a bad solenoid or there is dirt in the valve body causing the issue